This proposal is to develop a novel photoacoustic sensor for the noninvasive and continuous monitoring of the intracranial pressure (ICP) of patients with head or brain injury. The technique can measure the ICP changes to an accuracy of better than 0.5 mmHg, providing an important cerebral physiological parameter for diagnosis, clinical assessment and care of patient at emergency site, hospital and home. ICP monitoring is achieved through the high resolution (15 microM) detection of the shift of the blood vessel layer in the subarachnoid space by measuring the transit time of the photoacoustic signal. This signal is generated by the thermal stress of tissue through the absorption of a pseudo-random modulated (PRM) near IR illumination. The sensor employs SESI's proprietary PRM and resolution enhancement technique to achieve high resolution and continuous measurement without subjecting the tissue to radiation damage. Following the feasibility study in Phase I using a brain tissue and blood vessel phantom, a rugged and portable prototype will be developed in Phase II for clinical test in collaboration with a medical research group. The sensor will be integrated with other noninvasive diagnostic techniques for detection of local ICP elevation, brain hematoma or edema. PROPOSED COMMERCIAL APPLICATION: Commercial applications for the sensor is very promising. It can be used at emergency site, emergency unit, intensive care unit, physiological studies, and clinical patient management for ICP monitoring, blood oximetry and cerebral diagnosis.